In the office environment numerous documents are generated for which copies are required from time to time but yet copying of same is desired to be limited. For example, some employees may be granted temporary access to certain confidential documents but they are not permitted to make copies of them. Other employees in this office may have authorization to make copies of these confidential documents. It would therefore be desirable to provide a copier with the ability to determine if a document is confidential and limit access to copying to those authorized to copy same yet allow copying of non-confidential documents.
In the prior art as represented by U.S. Pat. No. 4,603,970, it is recognized that confidential documents may be distinguished by providing them with a metal so that copying of the confidential documents can be inhibited. In order to detect a confidential document a proximity detector is provided that moves relative to the document. A problem with such a copier is that productivity is lowered due to waiting time required for the proximity detector to traverse its fixed course so as to scan the entire document for any metal. Although it is recognized that the detector can remain stationary in those copiers using a document supporting platen glass that moves, such copiers are also relatively low in productivity.
It is, therefore, an object of the invention to provide a secure copier with relatively higher productivity capabilities than that suggested by the above prior art